Preparation method of one-step sequence-controlled hydroxy acid block copolyester

Abstract

The invention relates to the technical field of high polymer materials, in particular to a one-step sequence-controlled hydroxy acid block copolyester preparation method, which comprises: carrying out amine catalysis on mandelic acid and bromoacetyl bromide in acetonitrile to form ester, cyclizing with sodium bicarbonate in N, N-dimethylformamide, and recrystallizing to obtain PDD; the preparation method comprises the following steps: carrying out Mannich reaction on 2, 4-di-tert-butylphenol to obtain a ligand H3L, complexing the ligand H3L with zirconium alkoxide, and carrying out methyl lactate treatment to obtain [ONOO]-Zr; pDD and epsilon-caprolactone are heated and polymerized in the presence of a [ONOO]-Zr catalyst, benzoic acid is terminated, and precipitation and purification are performed to obtain sequence-controlled block copolyester P (PDD-b-CL). Compared with other sequence-controlled block copolymer synthesis methods, the one-step sequence-controlled hydroxy acid block copolyester preparation method provided by the invention has the advantages of mild reaction conditions and simplicity and convenience in operation.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a one-step method for preparing sequence-controlled hydroxy acid block copolyesters. Background Technology

[0002] With the continuous development of society and the economy, the global demand for plastic products is increasing daily. Some studies predict that plastic production will double within the next twenty years. However, most of the plastics currently in widespread use are derived from petroleum-based polymers. These materials are difficult to degrade in the natural environment and are difficult to recycle, resulting in serious problems of "white pollution" and resource waste.

[0003] Against this backdrop, polyester materials, possessing both biocompatibility and biodegradability, have demonstrated great potential as an environmentally friendly polymer to replace traditional petroleum-based plastics, helping to alleviate environmental pressure at its source. Among them, polycaprolactone (PCL), due to its excellent biocompatibility and complete biodegradability, is considered one of the ideal alternatives to petroleum-based plastics, with broad application prospects in biomedical engineering and environmental materials. However, PCL's inherently low glass transition temperature significantly limits its application in environments requiring high temperatures, such as hot beverage straws, heat-resistant packaging, and artificial blood vessels. Therefore, thermal property modification of PCL has become one of the key research focuses in this field.

[0004] Existing technologies demonstrate that copolymerizing caprolactone with other monomers possessing rigid structures is a feasible way to effectively improve the thermal properties of polycaprolactone. Block copolymers, in particular, often exhibit superior performance compared to random copolymers or simple homopolymer mixtures due to their unique sequence structure. Currently, conventional methods for synthesizing such sequence-controllable block copolyesters mainly include one-pot multi-step methods and multi-pot sequential feeding methods. Although these methods can achieve the preparation of the target product, they generally suffer from problems such as cumbersome synthesis steps, complex process control, and low production efficiency. Summary of the Invention

[0005] This application provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters to solve the problems of cumbersome synthesis steps, complex process control, and low production efficiency in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters, comprising the following steps: (1) Preparation of PDD: Under an inert atmosphere, mandelic acid was dissolved in acetonitrile, triethylamine was added, and an acetonitrile solution of bromoacetyl bromide was added dropwise under ice-water bath conditions. After the addition was complete, the reaction was stirred at room temperature. After the reaction was completed, the solvent was removed, ethyl acetate was added, and the mixture was washed successively with sodium bicarbonate solution, hydrochloric acid solution, and saturated brine. After drying, the mixture was filtered and concentrated to obtain the intermediate product. The intermediate product was dissolved in N,N-dimethylformamide and added dropwise to an N,N-dimethylformamide solution containing sodium bicarbonate. The mixture was stirred at room temperature. After the reaction was completed, the solvent was removed by vacuum distillation. Ethyl acetate was added, and the mixture was washed successively with hydrochloric acid solution and saturated brine solution. After drying, the mixture was filtered and concentrated. The crude product was recrystallized to obtain PDD. (2) Preparation of [ONOO]-Zr catalyst: 2,4-Di-tert-butylphenol, aqueous formaldehyde solution and hexamethylenetetramine were mixed and heated under reflux. After cooling, methanol was added and reflux was continued. After cooling to room temperature, the mixture was filtered and the filter residue was washed with methanol to obtain ligand H3L. Under an inert atmosphere, H3L and Zr(O) i Pr)4· i PrOH was dissolved in toluene and reacted with stirring at room temperature. After the reaction was completed, the solvent was removed and the crude product was recrystallized to obtain the precursor. The precursor was reacted with methyl lactate in toluene at room temperature. After the reaction was completed, the solvent was removed, and the crude product was recrystallized to obtain [ONOO]-Zr. (3) Sequence-controlled P(PDD- b Preparation of -CL): like Figure 1 As shown, the PDD prepared in step (1) and the [ONOO]-Zr prepared in step (2) are mixed with ε-caprolactone in a certain proportion and stirred under heating conditions. After the reaction is completed, benzoic acid solution is added to terminate the reaction. After precipitation, dissolution, and reprecipitation purification, the sequence-controlled block copolyester P (PDD-b-CL) is obtained after vacuum drying.

[0007] It should be noted that sequence-controlled P(PDD-) b -CL), the structure is as follows: .

[0008] Preferably, the molar ratio of mandelic acid, triethylamine, bromoacetyl bromide and sodium bicarbonate in step (1) is 164.5:167:164:288.9.

[0009] Preferably, the sodium bicarbonate solution in step (1) has a mass concentration of 5%, and the hydrochloric acid solution has a concentration of 2M.

[0010] Preferably, in step (2), the molar ratio of 2,4-di-tert-butylphenol, formaldehyde aqueous solution and hexamethylenetetramine is 16:16:1.3, the reaction temperature is 120°C, the reaction time is 72 h, and the recrystallization temperature is -20°C.

[0011] Preferably, the H3L and Zr(O) in step (2) i Pr)4· i The molar ratio of PrOH is 1:1.1, and the recrystallization temperature is -20℃.

[0012] Preferably, in step (3), the molar ratio of PDD, ε-caprolactone and [ONOO]-Zr is (20–150):(20–150):1, the reaction temperature is 40℃, and the reaction time is 6–168h.

[0013] This application also proposes a sequence-controlled hydroxy acid block copolyester, which is prepared by a one-step method for preparing sequence-controlled hydroxy acid block copolyester.

[0014] The beneficial effects achieved by using the present invention described above are as follows: 1. This invention utilizes the synergistic effect of a carefully designed [ONOO]-Zr catalyst and PDD monomer, and leverages the strong coordination ability between the benzene ring of the PDD side chain and the metal center of the catalyst to preferentially polymerize it in the reaction system. Thus, under the condition of only one feeding, it spontaneously achieves PDD priority and ε-CL subsequent sequence control, directly obtaining a copolymer with a regular block structure, overcoming the bottleneck of the traditional one-step method that is difficult to achieve sequence control. 2. The method of the present invention internalizes complex sequence control into the reaction mechanism of catalyst and monomer. The prepared block copolymer not only has excellent biocompatibility and biodegradability, but also has broad application prospects in biomedicine, food packaging and other fields. In addition, there is no need to add monomers, switch reaction conditions or separate and purify intermediate products, which greatly simplifies the operation steps and reduces energy consumption and time costs. 3. This invention benefits from the precise introduction of the PDD rigid benzene ring structure into the polymer chain segment, and the resulting regular block structure significantly improves the glass transition temperature and thermal decomposition temperature of the copolyester, successfully overcoming the inherent defect of poor thermal stability. This solves the problems of cumbersome synthesis steps, complex process control, and low production efficiency in existing technologies. Attached Figure Description

[0015] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 The P(PDD-) provided in the embodiments of the present inventionb A schematic diagram of the molecular structure of the preparation method of -CL); Figure 2 The P(PDD-) provided in the embodiments of the present invention b -CL) 1 HNMR spectrum; Figure 3 The P(PDD-) provided in the embodiments of the present invention b -CL) 13 CNMR spectrum; Figure 4 The P(PDD-) provided in the embodiments of the present invention b -CL) TG spectrum; Figure 5 The P(PDD-) provided in the embodiments of the present invention b DSC spectrum of -CL). Detailed Implementation

[0016] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0017] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0018] The following describes a one-step method for preparing a sequence-controlled hydroxy acid block copolymer according to embodiments of this application, with reference to the accompanying drawings. Addressing the low conversion efficiency mentioned in the background section, this application provides a one-step method for preparing a sequence-controlled hydroxy acid block copolymer. In this method, the synergistic effect of the [ONOO]-Zr catalyst and the PDD monomer is utilized to achieve sequence control with PDD priority and ε-CL subsequent in a single feed, simplifying operation and reducing costs. The prepared regular block copolymer exhibits excellent biocompatibility, biodegradability, and high heat resistance, solving the problems of cumbersome synthesis, complex control, and low efficiency in existing technologies, and has broad application prospects in multiple fields.

[0019] The present invention will be further described in conjunction with the following embodiments.

[0020] Example 1 This invention provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters, comprising the following steps: (1) Preparation of PDD In an argon atmosphere, first D , L Mandelic acid (25.00 g, 164.5 mol) was added to a round-bottom flask containing 250 mL of acetonitrile, followed by triethylamine (16.87 g, 167 mmol). The flask was placed in an ice-water bath at 0 °C with stirring. Then, a bromoacetyl bromide / acetonitrile solution (33.07 g / 100 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by rotary evaporation. Ethyl acetate was added, and the organic phase was washed with 5% sodium bicarbonate solution, 5% hydrochloric acid solution, and saturated brine, respectively. The mixture was then dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was removed by rotary evaporation. The resulting product did not require purification and was directly added to the next reaction step.

[0021] Sodium bicarbonate (5.00 g, 59.50 mmol) was added to a round-bottom flask, followed by DMF (400 mL). The product from the previous step (7.7 g, 28.30 mol) was dissolved in DMF (100 mL) and slowly added dropwise to the round-bottom flask. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the DMF was removed by vacuum distillation. Then, ethyl acetate was added, and the organic phase was washed with 2 M hydrochloric acid solution and saturated brine, respectively, and dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was evaporated to dryness. The resulting primary product was recrystallized from chloroform and toluene at low temperature before use.

[0022] (2) Preparation of [ONOO]-Zr 2,4-Di-tert-butylphenol (33.0 g, 0.16 mol), formaldehyde aqueous solution (4.84 g), and hexamethylenetetramine (1.88 g, 0.013 mol) were added to a round-bottom flask and heated to reflux at 120 °C for 72 h. After the reaction was completed, 100 mL of methanol was added and refluxed after the temperature dropped to 45 °C. After the temperature dropped to room temperature, the residue was collected by filtration and washed twice with methanol until it turned white, thus obtaining H3L.

[0023] Under an argon atmosphere, H3L (0.67 g, 1.0 mmol) and Zr(O) were... i Pr)4 i PrOH (0.43 g, 1.1 mmol) was added to a Shrek flask, followed by toluene, and the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by pumping dry, and the crude product was recrystallized from n-hexane at -20 °C. The purified product was a white solid. The obtained white solid (0.41 g, 0.5 mmol) and methyl lactate (0.24 mL, 2.5 mmol) were added together to a Shrek flask containing toluene (20 mL), and the mixture was stirred overnight at room temperature. The solvent was then removed by pumping dry, and the crude product was recrystallized twice from n-hexane at low temperature (-20 °C). The resulting white solid was [ONOO]-Zr.

[0024] (3) Sequence-controlled P(PDD- b Preparation of -CL) PDD, ε-CL, and [ONOO]-Zr were added to a pressure-resistant flask in a molar ratio of 20:20:1. The mixture was heated and stirred at 40°C for 3 days. After the reaction was complete, benzoic acid solution was added dropwise. A small amount of the reaction solution was taken to measure the reaction conversion rate. Then, n-hexane was added dropwise to the reaction solution until no precipitate formed. The supernatant was removed, and the precipitate was dissolved in dichloromethane. This process was repeated 2-3 times to remove unreacted PDD, [ONOO]-Zr, ε-CL, and a small amount of solvent. The final precipitate was dried under vacuum to obtain the sequence-controlled P(PDD- b -CL).

[0025] Example 2 This invention provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters, comprising the following steps: (1) Preparation of PDD In an argon atmosphere, first D , LMandelic acid (25.00 g, 164.5 mol) was added to a round-bottom flask containing 250 mL of acetonitrile, followed by triethylamine (16.87 g, 167 mmol). The flask was placed in an ice-water bath at 0 °C with stirring. Then, a bromoacetyl bromide / acetonitrile solution (33.07 g / 100 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by rotary evaporation. Ethyl acetate was added, and the organic phase was washed with 5% sodium bicarbonate solution, 5% hydrochloric acid solution, and saturated brine, respectively. The mixture was then dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was removed by rotary evaporation. The resulting product did not require purification and was directly added to the next reaction step.

[0026] Sodium bicarbonate (5.00 g, 59.50 mmol) was added to a round-bottom flask, followed by DMF (400 mL). The product from the previous step (7.7 g, 28.30 mol) was dissolved in DMF (100 mL) and slowly added dropwise to the round-bottom flask. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the DMF was removed by vacuum distillation. Then, ethyl acetate was added, and the organic phase was washed with 2 M hydrochloric acid solution and saturated brine, respectively, and dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was evaporated to dryness. The resulting primary product was recrystallized from chloroform and toluene at low temperature before use.

[0027] (2) Preparation of [ONOO]-Zr 2,4-Di-tert-butylphenol (33.0 g, 0.16 mol), formaldehyde aqueous solution (4.84 g), and hexamethylenetetramine (1.88 g, 0.013 mol) were added to a round-bottom flask and heated to reflux at 120 °C for 72 h. After the reaction was completed, the temperature was lowered to 45 °C and then 100 mL of methanol was added for reflux. After the temperature was lowered to room temperature, the residue was collected by filtration and washed twice with methanol until it turned white, thus obtaining H3L.

[0028] Under an argon atmosphere, H3L (0.67 g, 1.0 mmol) and Zr(O) were... i Pr)4 i PrOH (0.43 g, 1.1 mmol) was added to a Shrek flask, followed by toluene, and the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by pumping dry, and the crude product was recrystallized from n-hexane at -20 °C. The purified product was a white solid. The obtained white solid (0.41 g, 0.5 mmol) and methyl lactate (0.24 mL, 2.5 mmol) were added together to a Shrek flask containing toluene (20 mL), and the mixture was stirred overnight at room temperature. The solvent was then removed by pumping dry, and the crude product was recrystallized twice from n-hexane at low temperature (-20 °C). The resulting white solid was [ONOO]-Zr.

[0029] (3) Sequence-controlled P(PDD- b Preparation of -CL) PDD, ε-CL, and [ONOO]-Zr were added to a pressure-resistant flask in a molar ratio of 50:50:1. The mixture was heated and stirred at 40°C for 5 days. After the reaction was complete, benzoic acid solution was added dropwise. A small amount of the reaction solution was taken to measure the reaction conversion rate. Then, n-hexane was added dropwise to the reaction solution until no precipitate formed. The supernatant was removed, and the precipitate was dissolved in dichloromethane. This process was repeated 2-3 times to remove unreacted PDD, [ONOO]-Zr, ε-CL, and a small amount of solvent. The final precipitate was dried under vacuum to obtain the sequence-controlled P(PDD- b -CL).

[0030] Example 3 This invention provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters, comprising the following steps: (1) Preparation of PDD In an argon atmosphere, first D , L Mandelic acid (25.00 g, 164.5 mol) was added to a round-bottom flask containing 250 mL of acetonitrile, followed by triethylamine (16.87 g, 167 mmol). The flask was placed in an ice-water bath at 0 °C with stirring. Then, a bromoacetyl bromide / acetonitrile solution (33.07 g / 100 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by rotary evaporation. Ethyl acetate was added, and the organic phase was washed with 5% sodium bicarbonate solution, 5% hydrochloric acid solution, and saturated brine, respectively. The mixture was then dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was removed by rotary evaporation. The resulting product did not require purification and was directly added to the next reaction step.

[0031] Sodium bicarbonate (5.00 g, 59.50 mmol) was added to a round-bottom flask, followed by DMF (400 mL). The product from the previous step (7.7 g, 28.30 mol) was dissolved in DMF (100 mL) and slowly added dropwise to the round-bottom flask. After the addition was complete, the mixture was stirred overnight at room temperature. After the reaction was complete, the DMF was removed by vacuum distillation. Then, ethyl acetate was added, and the organic phase was washed with 2 M hydrochloric acid solution and saturated brine, respectively, and dried overnight with anhydrous MgSO4. The mixture was filtered and the ethyl acetate was evaporated to dryness. The resulting primary product was recrystallized from chloroform and toluene at low temperature before use.

[0032] (2) Preparation of [ONOO]-Zr 2,4-Di-tert-butylphenol (33.0 g, 0.16 mol), formaldehyde aqueous solution (4.84 g), and hexamethylenetetramine (1.88 g, 0.013 mol) were added to a round-bottom flask and heated to reflux at 120 °C for 72 h. After the reaction was completed, the temperature was lowered to 45 °C and then 100 mL of methanol was added for reflux. After the temperature was lowered to room temperature, the residue was collected by filtration and washed twice with methanol until it turned white, thus obtaining H3L.

[0033] Under an argon atmosphere, H3L (0.67 g, 1.0 mmol) and Zr(O) were... i Pr)4 i PrOH (0.43 g, 1.1 mmol) was added to a Shrek flask, followed by toluene, and the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was removed by pumping dry, and the crude product was recrystallized from n-hexane at -20 °C. The purified product was a white solid. The obtained white solid (0.41 g, 0.5 mmol) and methyl lactate (0.24 mL, 2.5 mmol) were added together to a Shrek flask containing toluene (20 mL), and the mixture was stirred overnight at room temperature. The solvent was then removed by pumping dry, and the crude product was recrystallized twice from n-hexane at low temperature (-20 °C). The resulting white solid was [ONOO]-Zr.

[0034] (3) Sequence-controlled P(PDD- b Preparation of -CL) PDD, ε-CL, and [ONOO]-Zr were added to a pressure-resistant flask in a molar ratio of 100:100:1. The mixture was heated and stirred at 40°C for 7 days. After the reaction was complete, benzoic acid solution was added dropwise. A small amount of the reaction solution was taken to measure the reaction conversion rate. Then, n-hexane was added dropwise to the reaction solution until no precipitate formed. The supernatant was removed, and the precipitate was dissolved in dichloromethane. This process was repeated 2-3 times to remove unreacted PDD, [ONOO]-Zr, ε-CL, and a small amount of solvent. The final precipitate was dried under vacuum to obtain the sequence-controlled P(PDD- b -CL).

[0035] Comparative Example 1 Under an argon atmosphere, ε-caprolactone and [ONOO]-Z were added to a pressure-resistant bottle at a molar ratio of 50:1, and the mixture was stirred at 40°C for 48 hours. After the reaction was completed, benzoic acid solution was added dropwise to terminate the reaction. The product was purified by precipitation with n-hexane, dissolution with dichloromethane, and reprecipitation. After vacuum drying, PCL homopolymer was obtained.

[0036] Comparative Example 2 Under an argon atmosphere, PDD, ε-caprolactone, and stannous octoate were added to a pressure vessel in a molar ratio of 50:50:1, and the mixture was stirred at 100°C for 12 hours. After the reaction was completed, the product was purified by precipitation in hexane, dissolution in dichloromethane, reprecipitation, and vacuum drying to obtain the random copolymer P(PDD- r -CL).

[0037] Performance testing The products prepared in Examples 1-5 of this invention were subjected to structural and performance characterization analyses, as follows: like Figure 2 and3 As shown, the product of Example 1 1 HNMR and 13 The HNMR spectra all showed sharp, single signal peaks. Specifically, the P(PDD-b-CL) peaks were... 1 The signal at chemical shift δ = 4.06 ppm in the HNMR spectrum can be attributed to the hydrogen at position 5 of the polymer backbone. This characteristic peak is a triplet, sharp in shape, and without any nearby error sequence signals, indicating that the prepared P(PDD-b-CL) sequence structure is regular. The P(PDD-b-CL) sequence... 13 The HNMR spectrum of the polymer backbone carbons mostly shows a single sharp peak, indicating that the prepared block copolymer has a regular sequence structure. Because in a regular chain sequence, equivalent carbon atoms are in a homogeneous chemical environment, there are no signals from erroneous sequences. Therefore, 13 The absence of broadened or multiple signals belonging to the random sequence in the carbonyl carbon region during HNMR analysis confirms the successful acquisition of a block copolymer with a regular sequence, rather than the random structure of Comparative Example 2.

[0038] As shown in Table 1 below, the molecular weight distribution of the products in all examples is less than 1.5, indicating that the polymerization process has good controllability. In contrast, the molecular weight distribution of Comparative Example 2 is wider.

[0039]

[0040] like Figure 4 As shown, the thermal decomposition temperature of the product in the example is significantly higher than that of PCL in Comparative Example 1 (approximately 270°C), reaching 293°C, demonstrating that the introduction of PDD blocks greatly improves the thermal stability of the material.

[0041] like Figure 5 As shown, the DSC curves of the products from the examples exhibit a separate glass transition temperature and a melting enthalpy. The glass transition temperature corresponds to the PCL-enriched phase (approximately -60°C). The glass transition temperature of the polymer is higher than that of PCL, indicating that the synthesized block copolymer effectively improves the thermal properties of PCL. Comparative Example 1, however, only shows the glass transition temperature of PCL. Furthermore, the glass transition temperature of the PDD phase in the examples is significantly higher than that of PCL, demonstrating a fundamental improvement in its heat resistance.

[0042] This application provides a one-step method for preparing sequence-controlled hydroxy acid block copolyesters. Utilizing the synergistic effect of a carefully designed [ONOO]-Zr catalyst and PDD monomer, and relying on the strong coordination ability between the benzene rings of the PDD side chain and the metal center of the catalyst, the method achieves sequence control of PDD preferential polymerization followed by ε-CL polymerization in a single feed, directly preparing copolymers with regular block structures. This method overcomes the traditional bottleneck of one-step methods that struggle to achieve sequence control. This method eliminates the need for adding monomers, switching reaction conditions, or separating intermediate products, significantly simplifying operations and reducing energy consumption and time costs. Furthermore, the resulting copolymers, due to the precise introduction of the rigid benzene rings from the PDD, possess excellent biocompatibility, biodegradability, and improved thermal stability. This effectively solves the problems of cumbersome synthesis steps, complex process control, low production efficiency, and poor thermal stability in existing technologies, and has broad application prospects in fields such as biomedicine and food packaging.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A process for the preparation of a sequence controlled hydroxy acid block copolyester in one step, characterized in that, The method comprises the following steps: (1) Preparation of PDD: Under the protection of inert atmosphere, mandelic acid is dissolved in acetonitrile, triethylamine is added, and a solution of bromoacetyl bromide in acetonitrile is added dropwise under the condition of ice water bath, and the reaction is stirred at room temperature after the dropwise addition is completed; after the reaction is completed, the solvent is removed, ethyl acetate is added, and the mixture is washed with sodium bicarbonate solution, hydrochloric acid solution and saturated brine in sequence, and then filtered, concentrated and dried to obtain an intermediate product; The intermediate product is dissolved in N,N-dimethylformamide, and is added dropwise into a solution of sodium bicarbonate in N,N-dimethylformamide, and the reaction is stirred at room temperature; after the reaction is completed, the solvent is removed by distillation under reduced pressure, ethyl acetate is added, and the mixture is washed with hydrochloric acid solution and saturated brine in sequence, and then filtered, concentrated and dried, and the obtained crude product is recrystallized to obtain PDD; (2) Preparation of [ONOO]-Zr catalyst: 2,4-di-tert-butylphenol, formaldehyde aqueous solution and hexamethylenetetramine are mixed and heated to reflux, methanol is added after cooling, and the mixture is refluxed, and then filtered after cooling to room temperature, and the residue is washed with methanol to obtain ligand H3L; H3L was dissolved in toluene under inert atmosphere, and Zr(O i Pr)4 was added. The reaction mixture was stirred at room temperature. After the reaction was completed, the solvent was removed, and the crude product was recrystallized to obtain the precursor. i PrOH was dissolved in toluene, and the reaction was stirred at room temperature. After the reaction was completed, the solvent was removed, and the crude product was recrystallized to obtain the precursor. The precursor and methyl lactate are reacted in toluene at room temperature, the solvent is removed after the reaction is completed, and the crude product is recrystallized to obtain [ONOO]-Zr; (3) Sequence-controlled P(PDD- b Preparation of -CL): The PDD prepared in step (1) and the [ONOO]-Zr prepared in step (2) are mixed with ε-caprolactone in a certain proportion, and the mixture is stirred under heating, the reaction is terminated by adding benzoic acid solution after the reaction is completed, and then the mixture is purified by precipitation, dissolution and re-precipitation, and vacuum dried to obtain a sequence-controlled block copolyester P (PDD-b-CL).

2. The process for the preparation of a one-step sequence of controlled hydroxy acid block copolyesters according to claim 1, characterized in that, In step (1), the molar ratio of the mandelic acid, triethylamine, bromoacetyl bromide and sodium bicarbonate is 164.5:167:164:288.

9.

3. The process for the preparation of a one-step sequence of controlled hydroxy acid block copolyesters according to claim 1, characterized in that, In step (1), the mass concentration of the sodium bicarbonate solution is 5%, and the concentration of the hydrochloric acid solution is 2M.

4. The process for the preparation of a one-step sequence of controlled hydroxy acid block copolyesters according to claim 1, characterized in that, In step (2), the molar ratio of the 2,4-di-tert-butylphenol, formaldehyde aqueous solution and hexamethylenetetramine is 16:16:1.3, the reaction temperature is 120°C, the reaction time is 72h, and the recrystallization temperature is -20°C.

5. The process for the preparation of a one-step sequence of controlled hydroxy acid block copolyesters according to claim 1, characterized in that, H3L and Zr(O i Pr)4· i at a molar ratio of 1:1.1 and at a recrystallization temperature of -20°C.

6. The process for the preparation of a one-step sequence of controlled hydroxy acid block copolyesters according to claim 1, characterized in that, In step (3), the molar ratio of the PDD, ε-caprolactone and [ONOO]-Zr is (20-150):(20-150):1, the reaction temperature is 40°C, and the reaction time is 6-168h.

7. A sequence controlled hydroxy acid block copolyester characterized by, It is prepared by the method for preparing a sequence-controlled hydroxy acid block copolyester of one-step method according to any one of claims 1 to 6.

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